In the gas industry, it is highly desirable in many instances that the pressure in well bores penetrating subterranean formations be determinable quickly and accurately. For instance, it is possible to determine certain parameters of the formation such as the permeability, and the like by measurement of pressure changes as a function of time. In some instances, it is desirable to know the pressure in a well bore in order that the migration of gases into lower pressure formations may be avoided or controlled. As a result, several devices have been proposed for measuring the pressure in subterranean formations penetrated by a well bore.
Previously developed systems have utilized monitoring devices in which the device is lowered into the well bore using a cable or string. Such devices are described in U.S. Pat. No. 3,874,231 issued to Walther, Jr., on Apr. 1, 1975 and entitled "Diffusion Bearer Chamber For Sperry Sun Permagage Type Pressure Gauge" and U.S. Pat. No. 4,267,726 issued to Noik on May 19, 1981 and entitled "Well Pressure Testing Method".
Such previously developed gas well monitoring devices have suffered from the physical consequences of measuring such pressure in the well bore itself. For example, due to the corrosive nature of the elements present in the well bore, such monitoring devices suffer structural degradation and failure in use. Such devices when present within the well bore undergo substantial movement and friction such that the device may sever from the cable and be lost in the well. Additionally, where the well bore is not substantially vertical, but irregularly shaped or curved, such monitoring devices may be difficult to remove from the well.
A need has thus arisen for an improved gas well monitoring device for computing bottom hole pressure of a well bore having improved reliability and accuracy. A need has further arisen for a gas well monitoring device which eliminates the difficulties in using such previously developed devices which are lowered into the well bore. Furthermore, a need has arisen for a gas well monitoring device which automatically and periodically samples bottom hole pressures for subsequent display or storage.